Rheostat.



PATENTED 11:11.13, 1906.(

F. L. STONE, RHBOSTAT. APPLIGATION FILED 1111125.19011.

Fig. I.

lnvenn FRED LTONE. 5y Mu/6, @M4

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to one side of the electric circuit and UNTTED lsTATEs PATENT OFFICE.

FRED L- STONE, yor scHENncTAnY, NEWLYoRK, AssiGn-aa Tc' `('ENERpH,

`ELECTRIC COMPANY, A CORPORATION .OF .NEWYORKZY l y I l RHEosTA-r To a/ZY, whcm 4itv may concern/ Be it known thatI ,FRED L. STONE, a subject of the King of Great Britain, residing at- Schenectady,

, The rheostats in common use Icomprise" av resistance-conductor I,connected at one end PTQ vided at vcertain intervals of its length with viiXed' contact-studs and a 'movable contact part connected to the opposite side .of the circuit and adapted to be stepped from contactstud to contact-studto complete the circuit through a greater or less number of sections of they resistance-conductor. As the movable contact member steps from one independent contact-'stud to another more or less A 4electric sparking takes place, which very soon .pits and roughens the contact-surfaces, caus- 'lng the movable contact lto cling .and move with irregularity and producing fluctuations in the current. The ob'ect of my invention is to provide a vhi hly-e cient rheostatl in which the movabgle` contact may'pass with facilit from one extreme position`y to the other wit out interru tion or sparking ofthe electric circuit.

n carrying out myinventionl mount upon an insulating-support a plurality of-parallel resistance-conductors connected in series and shunt-circuit the several pairs of the resistance-conductors by short bridging-contacts 'mounted on a suitable insulated sup or't arranged to travel the length of the condhctors.

For a more complete understanding of my invention reference may be had to the following detailed description and the accompanytion, in whichy Figure 1 is a plan of a rheostat embodying one form of my invention, and Fig. 2 is a centra'l transverse section of the same.

Y. ing drawings, forming a part lof this 'sp'ecifica- The base consists of-a rectangular slab 1, of

stone, porcelain, or composition, provided with suitable apertures 2 for the reception of screws by which it is secured in position.

The resistance-conductor consists of `a lurvality of flat bars or strips 3 to 10 of nic el,

lsteel, or other material "of low conductivity bent into the form of nearly complete circles y Specification of Letters Patent. Application filed `July 25 1904.l Serial No. 218,\l31. y

clip 15 secured to one side thereof.

' Patented Feb. 13,1906.

l of progressively-increased diameter and concentrically arranged in grooves in theupper" The outermost surface of. the baseplate. strip 10 has one end ilkbent radially outward 4and secured to a terminal post 12 .and the other end i'olded in and connected to the corresponding end of the adjacent strip 9, the opposite end of the latter strip being similarly connected to strip 8, and. so on in series to the end of the innermost strip 3, which is vconnected to a ring-contact 13, also secured in a concentric groove in the top surface of 4 the base. Concentrically arranged in a grooveoutside the bars 3 to 1() is a-segm'ental contact-ling 14, having a terminal binding- A second terminal binding-clip 16 is mountedfon the base adjacent to the iirst binding-clip 15 and connected by a back conductor 17 to post 1 2,.whicl1 is provided with spring contact-fingers 18 for a purpose hereinafter set forth.

The movable contact consists of a plurality of spring-iingers 19 of U-shaped cross-section extending into the spaces between alternate bars or strips 3 to10 and pressing transversely against their sides. These fingers 19 arey secured to a 'block 2O of `insulation secured to the under side of an arm 21, pivoted upon a shaft 22, mounted upon the base concentrically with thestrips 3 to 110. The arm 21 carries at its-outer end a handle 23, by which it is actuated,and extending through the block 20 is a spring conducting rod or plate 24, adapted to engage at its respective ends with the inner and outer circular contacts 13 and 14. The outer end of the rod 24 is extended somewhat beyond the outside periphery of the larger contact 14, so'as lto enter between the spring-fingers 18 of the post 12. When the arm 21 is in the startin position a: the current passes from termina 16 through the back conductor 17, post 12, substantially the'full length of the resistanceconductor,to the inner contact-ring 13, contact-bar; 24', outer contact-ring 14, and terminal 15. As the arm 21 is moved counterclockwise more and more of the resistanceconductor is shunt-circuited by the contactfingers 19 so that when the arm reaches the position indicated inv Fig. 1 the lower half of the resistance-conductor strips 3 'to 10 will have been cut out of circuit. When the arm 21 arrives at .the full-on position yy, the cuter end of the contact-bar 24 engages the springfingers 1S on the post 12 and shunt?` ircuits the current directly from the post 1`2'to` the outer contact-ring 14, cutting out the whole of the resistance-conductor, so that no part thereof will be injured by excess of current, however long continued.

I do not desire terestrict myself to the par.- ticular form or arrangement of parte herein described and shown, since it is; apparent that they may be changed and modied witlr out departing from my invention.

What I claim as new, and desire to secure by Letters Patent of the United States, is

l. In a rheostet, the combination of a resistance-conductor comprising a series of pai allel strips or bars alternately connected in sets of two, and a movable member provided with a series of bridging-contacts eeclindapted to serially connect two adjacent sets of strips or bars.

2. In a. rheostat, the combination of im insulating-base, a. resistance-conductor eonirising a Aseries of circular parallel strips or bars mounted upon said base and alternately amen connected in sets ci' two. c. e concentrically-pivoted member ext Kling over said strips or bars and provided. with e series of spr1ng-contacts each ada ted to serially connect two sets of strips or 3. In a rheostet, the combination of en insulating-base, a resistenee-eondnctor comprising one or more pairs ot parallel circular bers or strips inountedon seid base, a concentric inner contact-ring connected to one end of said resista-nce member, an outer con'- oentric contect-1i11g and a concentricclly-pivoted member having one or more bridgingcontacts each adapted to engage e, pair of strips or bars, and n Contact rod or plete adapted to engage seid-inner and outer concentric rings.

In witness whereof I have hereunto set niy hand this 22d day oi July, i904.

. FRED L. STONE.

Witnesses BENJMUN B. HULL, HELEN OXFORD. 

